"Bill Wright" wrote in message
news
On 31/12/2017 17:46, NY wrote:

Another variable throw into the mix: not all black and white films on TV
are the same shade. The film base may develop a slight colour tint as it
ages, which leads to greys that may be very pale mauve or very pale
green. You'd think that when B&W films were transmitted on TV, they would
set R=G=B so as to achieve pure, untinted B&W irrespective of the colour
of the original film.

They used to be something called a colour killer that locked the telly to
monochrome when a monochrome prog was on. When it didn't work the picture
would have spurious colours, usually flashing. It was most annoying.

I realise that broadcasters used to turn off the colour carrier when a
monochrome programme was broadcast, though I imagine towards the end of
analogue TV, broadcast equipment might start to protest if the CSC was ever
not present.

For digital, I'm surprised that the source material direct from the telecine
doesn't have the three components set to equal values, long before it gets
as far as the broadcast equipment.

Talking Pictures TV shows a lot of B&W material and there is often a colour
cast - most noticeable when they change from one film to a trailer for
another at an advert break.